But the decisive rejection of Gray, 71, in Tuesday's Democratic primary in favor of challenger Muriel Bowser, a member of the D.C. City Council, also reflected a changing city. One that's wealthier, younger, whiter, and far less connected to traditional machine politics that old school pols like Gray rely on.

It would be a mistake to overstate the meaning of the low-turnout, multi-candidate primary that Bowser won with 44.3 percent of the vote to Gray's 32.4 percent, say those familiar with the city's politics.

Both Gray and Bowser are African American; there's little ideological distance between them. And Bowser, 41, who will run against an independent candidate in the November general election, was a protégé of former Mayor Adrian Fenty, a rising young African American political star until his loss to Gray four years ago.

Yet there are unmistakable signs of important — if incremental — changes in the political landscape, say Washingtonians LaTanya Brown-Robertson, an economist and D.C. demographic expert, and her husband, Diarra Robertson, a political scientist. Both are associate professors at Bowie State University outside Washington.

Here's how Brown-Robertson and her husband told us they view Bowser's win and the overwhelmingly Democratic city she's on track to lead. (For the record: both say they voted for Gray, but saw both candidates as capable.)

1. The city's most rapidly-gentrifying neighborhoods, those on the less affluent east side, still voted for Gray as they did four years ago, but in far fewer numbers.

"These are neighborhoods where there is population growth, where the millennials are moving in and where property values and gross adjusted income has been increasing more than the city median," Brown-Robertson says. "Gray held the majority in those neighborhoods, but the numbers are showing you that the demographics are changing."

Her research has shown that not only are the gentrifying neighborhoods younger, but there's been an increase in the number of people filing income tax returns as individuals, and a rapid growth in the number of people living in higher-density condominiums.

2. The results suggest a developing divide that goes beyond the issue of black and white, and points toward economic and generational divides.

"When you talk about gentrifying neighborhoods, you're talking more about a class issue than a black-and-white one. One thing Bowser focused on was improving middle schools in Washington – that's an indicator of the new D.C., and appeal by her to the gentrifiers," says Brown-Robertson, a native Washingtonian. "This is a conversation about having more people with bachelor's and graduate degrees moving into gentrifying neighborhoods, and their preferences."

3. The odor of scandal hanging over all of D.C. government, and the reality of a younger city, conspired to thwart not only Gray, but five-term City Councilman Jim Graham, 68, ousted by a young activist who capitalized on Graham's ethics lapses.

"A symbolic and generational page has been turned in terms of leadership," says Diarra Robertson. "The scandals have left a cloud over older, incumbent council members, and those with exposure from longtime service."

"This new page may mean that those with stronger connections with old D.C., or people with lower economic background could be forgotten about," he says. "For the overall prosperity of the city, though, it's a new page."

4. The primary results map looks stark, suggesting a city divided down the middle: Gray's traditional African American base holding, if barely, to the east, Bowser, like her mentor, Fenty, dominating in the wealthier, whiter western reaches.

But digging down, the experts say, the division is shallower than it was four years ago, and, like it or not, will continue to lessen as Washington's neighborhoods continue to change.

"From an economist's view, I'm happy because my property values are going up," says Brown-Robertson, who lives with her husband and five-year-old daughter in Brookland, one of Washington's gentrifying neighborhoods.

"From a social standpoint, I'm excited about the diversity," she says. "But it's important to understand the history and respect the longtime D.C. residents."

The primary, her husband asserts, says little about race. There might be more of a conversation on it in November, when Bowser runs against Independent David Catania, a white city council member.